Purification method of lithium difluorophosphate

A lithium difluorophosphate and purification method technology, which is applied in the field of lithium difluorophosphate purification, can solve the problems of high energy consumption, inability to effectively reduce product acidity, inability to remove acidic substances such as hydrofluoric acid, etc., and achieve low energy consumption Effect

Active Publication Date: 2019-06-28
JIANGSU GUOTAI SUPER POWER NEW MATERIALS
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Although Example 1 of this patent discloses that the free acid of the product is 65ppm, the free acid of Example 2 is 45ppm, but the free acid of Example 3 is 410ppm
In addition, the applicant has found through research that the patented method cannot reduce the acidity of the product very well. The acidity in Examples 1 and 2 of the patent is low, which is likely to be the raw material of the crude lithium difluorophosphate selected. Acidity is already at low levels
[0008] CN107381530A discloses a method for purifying lithium difluorophosphate. Although it discloses that the purity of the product can reach 99.97%, the patented method cannot effectively reduce the acidity of the product. In addition, it needs to evaporate the solvent to dryness, which consumes a lot of energy
[0009] CN107381531A discloses a preparation method of lithium difluorophosphate. The purification method mainly uses acetone to wash out insoluble impurities, and then obtains the finished product by evaporating the acetone solvent. The impurities dissolved in the solvent cannot be effectively removed, and the method Can not effectively reduce the acidity of the product
[0010] In summary, none of the above methods can remove acidic substances such as hydrofluoric acid in the product
In fine chemicals, especially lithium salt materials in lithium battery electrolytes have strict requirements on purity and acidity quality, if the purification problem of lithium difluorophosphate cannot be effectively solved, it will hinder the use of lithium difluorophosphate in the field of lithium batteries Further promotion and application of

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0044] Add 200g of ethanol and 21.6g (0.2mol) of crude lithium difluorophosphate (purity 98.1%, acidity 300ppm) into a 500mL reaction flask, and stir to dissolve. Put 1.0 g of lithium hydroxide into the bottle, blow dry nitrogen, and stir at 60° C. for 3 h. Insoluble materials were removed by filtration.

[0045] The treated solution was transferred and concentrated by evaporation under reduced pressure until the remaining 60 g of the solution was stopped, and 120 g of dichloromethane was added thereto, and stirred for 2 hours to crystallize. The obtained crystal weighed 19.5 g after vacuum drying to obtain a pure product. The yield of the purification method provided by Example 1 of the present invention is 90.3%, the acidity (HF) content in the pure product is 51ppm, and the purity is 99.95%. The purity was determined by ion chromatography, and the acidity was measured by titration.

Embodiment 2

[0047] Add 200g of acetone and 21.6g (0.2mol) of crude lithium difluorophosphate (purity 98.1%, acidity 300ppm) into a 500mL reaction flask, and stir to dissolve. Put 1.0 g of lithium oxide into the bottle, blow dry nitrogen, and stir at 50° C. for 2 h. Insoluble materials were removed by filtration.

[0048] The treated solution was transferred and concentrated by evaporation under reduced pressure until the remaining 80 g of the solution was stopped, 120 g of hexane was added thereto, and stirred for 3 hours to crystallize. The obtained crystal weighed 18.1 g after vacuum drying to obtain a pure product. The yield of the purification method provided by Example 2 of the present invention is 83.8%, the acidity (HF) content in the pure product is 43ppm, and the purity is 99.92%. The detection method of purity and acidity is with embodiment 1.

Embodiment 3

[0050] Add 150g of ethylene glycol dimethyl ether and 21.6g (0.2mol) of crude lithium difluorophosphate (purity 95.6%, acidity 1000ppm) into a 500mL reaction flask, and stir to dissolve. Put 2.0 g of lithium carbonate into the bottle, blow dry nitrogen, and stir at 80° C. for 4 h. Insoluble materials were removed by filtration.

[0051] The treated solution was transferred and concentrated by evaporation under reduced pressure until the remaining 60 g of the solution was stopped, 60 g of toluene was added thereto, and stirred for 3 hours to crystallize. The obtained crystal weighed 19.6g after vacuum drying to obtain a pure product. The yield of the purification method provided by Example 3 of the present invention is 90.7%, the acidity (HF) content in the pure product is 25ppm, and the purity is 99.98%. The detection method of purity and acidity is with embodiment 1.

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Abstract

The invention provides a purification method of lithium difluorophosphate. The purification method comprises the following steps: dissolving a lithium difluorophosphate coarse product in an organic solvent to obtain a coarse product solution; adding alkaline lithium salt into the coarse product solution, and filtering undissolved substances after heating to obtain a filtrate; carrying out evaporation and concentration on the obtained filtrate to remove part of the organic solvent to obtain concentrated liquor; and adding a low polarity organic solvent into the concentrated liquor for crystallization, and then filtering and drying the mixture to obtain a lithium difluorophosphate pure product. By removing acid in the lithium difluorophosphate coarse product with the alkaline lithium salt and filtering impurities, for example, lithium fluoride and excessive alkaline lithium salt, undissolved in the solvent by selecting a proper solvent and adjusting the polarity of the solvent for crystallization, lithium difluorophosphate, the purity of which reaches over 99.9% and the acidity of which is within 70 ppm to meet the using demand of a battery is obtained more simply. The yield of the purification method is over 85%, and the energy consumption is low.

Description

technical field [0001] The invention relates to a method for purifying lithium difluorophosphate. Background technique [0002] Lithium difluorophosphate has the characteristics of good thermal stability, hydrolysis resistance and good electrochemical stability. Adding lithium difluorophosphate to lithium-ion batteries can effectively improve the high and low temperature performance of the battery. The principle is that a layer can be formed at the electrode interface A low-resistance SEI film can suppress the decomposition of the electrode surface at the same time. [0003] The prior art discloses lithium monofluorophosphate (Li 2 PO 3 F) or lithium difluorophosphate (LiPO 2 f 2 ) additive electrolyte, wherein the additive can react with lithium to form a protective film on the surface of the positive or negative electrode, which can effectively inhibit the decomposition caused by the contact between the electrolyte and the electrode material, thereby inhibiting self-di...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C01B25/455H01M10/0567H01M10/0525
CPCY02E60/10
Inventor 王传水任齐都王冰桐陈周圆施苏萍
Owner JIANGSU GUOTAI SUPER POWER NEW MATERIALS
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